US7542498B2 - Semiconductor laser diode - Google Patents

Semiconductor laser diode Download PDF

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US7542498B2
US7542498B2 US11/195,792 US19579205A US7542498B2 US 7542498 B2 US7542498 B2 US 7542498B2 US 19579205 A US19579205 A US 19579205A US 7542498 B2 US7542498 B2 US 7542498B2
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cladding layer
refractive index
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semiconductor laser
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US20060187987A1 (en
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Etsuko Nomoto
Tsukuru Ohtoshi
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Lumentum Japan Inc
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Opnext Japan Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers

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  • the present invention relates to a semiconductor laser device.
  • the semiconductor laser device of the invention is particularly useful when it is used as a light source for information processing terminals or optical communication, etc.
  • Non-Patent Document 1 Non-Patent Document 1
  • JP-A No. 11-233883 Patent Document 1
  • Non-Patent Document 2 discloses introduction of two optical guiding layers 43 each comprising GaInP having negative strain in an AlGaInP n-cladding layer 6 as shown in FIG. 6 as a structure for simultaneously providing the increased output and narrowed vertical radiation angle of a light source for use in DVD recording.
  • the thickness and position of the two optical guiding layers 43 it is possible to provide a degree of freedom for the design of the light confinement coefficient in the active layer 7 having an effect on a threshold current value and an absorption loss in upper and lower GaAs layers, 13 , 1 , 2 having an effect on the slope efficiency. Accordingly, the vertical radiation angle can be narrowed with no trouble such as increase of the threshold carrier density.
  • Patent Document 1 JP-A No. 11-233883 (FIG. 5)
  • Non-Patent Document 2 Electronic Information Communication Society Technical Study Report Vol. 103, No. 523 (2003) (page 41)
  • the present invention intends to obtain a semiconductor laser device capable of suppressing the kink, lowering the loss and stabilizing the direction of polarization, with the light distribution being continuous in order to improve the characteristics of a light source for use in DVD recording.
  • the optical distribution is shifted toward the lower cladding layer in order to suppress the kink.
  • a laser using an AlGaInP material used for a light source for use in DVD recording since it has a refractive index waveguide structure with the extremely small difference of the refractive index between the cladding layer and the active layer, light confinement to the active layer decreases as the refractive index of the lower cladding layer approaches the refractive index of the active layer for suppressing kink.
  • the direction of polarization becomes instable and, for example, the oscillation plane of the electric field may sometimes be different from the surface of the active layer even under oscillation at a TE mode. While it is necessary that the direction of polarization is stable within the active layer surface in the DVD optical system, since it is more stable as the light confinement to the active layer increases, it is in a trade off relation with the condition for suppressing the kink. Accordingly, it is difficult to control the composition for satisfying them simultaneously and the process margin in the manufacture is decreased.
  • FIG. 6 In a semiconductor laser device adopting two optical guiding layers in an AlGaInP n-cladding layer as shown in FIG. 6 as a second example of the prior art, there is a likelihood for the design of the structure capable of simultaneously satisfying the suppression of the kink and the stabilization of the polarization direction which are in the trade off relation.
  • FIGS. 7A and 7B show an example of calculating the shape of the light distribution.
  • FIG. 7A shows a near field pattern in which the ordinates expresses the optical intensity and the abscissa expresses the position in the direction of the crystal stacking with the active layer as the center assuming the direction to the upper cladding layer as positive.
  • FIG. 7B is a far field pattern in which the ordinate expresses the optical intensity and the abscissa expresses the far field beam divergent angle. It can be seen that plural peaks are present in the near field images of FIG. 7A , and undesired effect such as skirting is given also on the shape of the far field images shown in FIG. 7B . In a case where plural optical spots are present, a large error may possibly be caused when signals are read and written by introducing laser light on DVD media. In view of the spots on the DVD media, it is desirable for continuous optical pattern not having extremal values at the positions other than the active layer position as shown in FIGS. 8A and 8B .
  • the invention intends to provide a semiconductor laser device enabling high power operation, having a structure capable of simultaneously suppressing the kink, reducing the loss, stabilizing the direction of polarization, and allowing the optical pattern to decrease monotonously with receding from the active layer, and enabling easy control of the crystal composition for the structure.
  • layers of high refractive index different from the cladding layer in view of the composition are introduced while being dispersed for a range larger than the spot size, in order to direct light to a lower cladding layer nearer to a crystal growing substrate of a semiconductor laser.
  • at least one of the introduced layers lies in the region where the electric field intensity is about 50% or more of the maximum value.
  • the introduced layers are dispersed for a wide range larger than the spot size at a distance sufficiently larger than the interlayer distance referred to as a super lattice and less than 1 ⁇ 4 of the spot size (that is, radius) in the vertical direction.
  • the spot size represents a distance from the maximal point of the emission intensity to a point at which the intensity is 1/e 2 adopted in the relevant technical field. Symbol e is the base of natural logarithm.
  • the distance between each of the layers is preferably made larger such that the states of electrons or holes do not overlap. Accordingly, this is different from the thickness in the case of a super lattice or multi-quantum well.
  • the introduced layer is the super lattice or multi-quantum well
  • confinement of carriers or light increases by the overlap of the state of electrons or holes. Therefore, since the optical density has a maximal value at the position, this hinders that the optical power in the near field changes continuously. Accordingly, the distance between the introduced layers is made large enough so that confinement of carriers or light does not increase excessively.
  • the distance between the introduced layers is decided such that the layers are introduced by at least four layers within the range of the spot size while the introduced layers receding as much as possible.
  • the refractive index and film thickness of the introduced layer smaller than the refractive index or film thickness of the active layer, it provides an effect of preventing the fact that the optical confinement of the introduced layer is made larger than the active layer and the change of the optical power in the near field is not continuous. It is also possible to make both of the refractive index and film thickness of the introduced layer smaller than those of the active layer. In the invention, it is not always necessary to space all the plural layers at an equal distance. In this regard, this is different from the structure in which semiconductor super lattice periodical thin film layer is disposed below the active layer as disclosed in JP-A No. 11-274635 (Patent Document 3).
  • the semiconductor laser device of the invention is as described below. That is, this can be said as a semiconductor laser device of a structure in which a cladding layer put between a semiconductor substrate and an active layer has a first cladding layer, a second cladding layer and a stacked body inserted between the first and the second cladding layer, and the stacked body having a layer having a refractive index higher than the refractive index of the first or the second cladding layers and comprising a material different from that of the first or the second cladding layer with a thickness of about electron de Broghie wavelength or less, and a layer having a refractive index substantially equal with that of the first or the second cladding layer stacked alternately is inserted with the total thickness of the first and the second cladding layers or more.
  • the refractive index may sometimes differ by about 0.001.
  • a combination of the first and the second cladding layers having refractive indexes different from each other by about 0.008 at maximum may also be adopted.
  • the composition for each of one of the layers of the stacked body to be insert has a value between the refractive indexes of the first and the second cladding layer, it is estimated as about 0.004 (to 0.15%) in view of the difference of the refractive index.
  • substantially the same refractive index is considered to be within such an extent of range.
  • the invention In the manufacture of the semiconductor laser device according to the invention, it is preferred to minimize the kinds of the compositions of crystals constituting the layered structure of the semiconductor laser device in order to improve the controllability for the composition and facilitate the detection in the inspection step.
  • Control is easiest in a structure where the refractive index is made equal between the upper cladding layer and the lower cladding layer excluding the introduced layer, the introduced layer has a lattice constant substantially equal to the cladding layer and has a film thickness smaller than that of the active layer and a refractive index smaller than that of the active layer.
  • the relationship between the thickness and refractive index of the introduced layer and those of the active layer is determined such that the optical confinement is largest in the active layer and the optical pattern is made continuous.
  • the electric field intensity distribution takes a maximum value at the position on the active layer, not takes a maximal value at the position on the introduced layer, and decreases monotonously as receding from the active layer.
  • the insertion position for the introduced layer may be decided as four or less position so as to satisfy a far field angle from 15° to 19° at the operating temperature suitable to a light source for use in DVD. In this case, the possibility that the electric field may take a maximal value at the introduction position is increased.
  • the positions for introduction are spaced apart and the number of the positions is increased to five or more.
  • the near field and far field patterns are calculated assuming that introduced layers are incorporated at 10 positions, it is shown as in FIGS. 8A and 8B .
  • the refractive index of the etch stopper layer for manufacturing a ridge structure is higher than the refractive index of the cladding layer, control can be conducted easily by making the refractive index of the introduced layer equal to that of the etch stopper layer.
  • the composition can be controlled easily when the introduced layer comprises GaInP. Even when it is designed such that the electric field intensity does not take a maximal point, appropriate optical confinement and fixing of the electric field direction to the horizontal direction occur and the direction of polarization can be stabilized in a horizontal state.
  • the invention can provide a semiconductor laser device capable of suppressing the kink in the output characteristics and satisfying stabilization for the direction of polarization. Further, the invention enables the optical distribution to obtain continuous characteristics.
  • FIG. 1 is a cross-sectional view of an AlGaInP system buried ridge type semiconductor laser according to a first embodiment of the present invention
  • FIG. 2 is a cross-sectional view of an AlGaInP system ridge type semiconductor laser according to a second embodiment of the present invention
  • FIG. 3 is a cross-sectional view of an AlGaAs/InGaAs system ridge type semiconductor laser according to a third embodiment of the present invention.
  • FIG. 4 is a cross-sectional view of an InGaAsP system buried hetero type semiconductor laser according to a fourth embodiment of the present invention.
  • FIG. 5 is a cross-sectional view of a ridge type semiconductor laser using an asymmetric cladding layer according to the prior art
  • FIG. 6 is a cross-sectional view of a ridge type semiconductor laser in which an optical guiding layer is inserted to a lower cladding layer according to the prior art
  • FIG. 7A shows a near field pattern in a semiconductor laser in which an optical guiding layer is inserted to a lower cladding layer
  • FIG. 7B shows a far field pattern in a semiconductor laser in which an optical guiding layer is inserted to a lower cladding layer
  • FIG. 8A shows a near field pattern in a semiconductor laser according to a invention.
  • FIG. 8B shows a far field pattern in a semiconductor laser according to a invention.
  • a semiconductor laser device in which the cladding layer in direct concern with the invention is either InP or In 1-x Ga x As y P 1-y , and a layer comprising the material different from the cladding layer comprises In 1-z-w Ga z Al w As (0 ⁇ z ⁇ 0.47 and 0 ⁇ w ⁇ 0.48), or In 1-x′ Ga x′ As y′ P 1-y′ (0 ⁇ x ⁇ x′ ⁇ 0.47 and 0 ⁇ y ⁇ y′ ⁇ 1) different, in view of the composition, from In 1-x Ga x As y P 1-y .
  • a semiconductor laser device in which the cladding layer in direct concern with the invention is either InP or In 1-z-w Ga z Al w As, and layer comprising the material different from the cladding layer comprises In 1-x Ga x As y P 1-y (0 ⁇ x ⁇ 0.47 and 0 ⁇ y ⁇ 1), or In 1-z′-w′ Ga z′ Al w′ As (0 ⁇ z ⁇ z′ ⁇ 0.47 and 0 ⁇ w′ ⁇ w ⁇ 0.4) different in view of the composition from In 1-z-w Ga z Al w As.
  • the semiconductor laser devices (1) and (2) above are semiconductor laser devices each having an oscillation wavelength of 1.3 ⁇ m to 1.55 ⁇ m band. They are usually used for optical communication.
  • the control is easy. For example, this is the same composition as that for the etch stopper layer in the ridge structure or a layer of high reflective index used as the diffraction grating of a distribution feedback laser.
  • a semiconductor laser device in which the cladding layer in direct concern with the invention comprises Al x Ga 1-x As (0 ⁇ x ⁇ 1), and the layer comprising the material different from the cladding layer comprises GaAs.
  • a semiconductor laser device in which the cladding layer in direct concern with the invention comprises Ga 0.52 In 0.48 P, and the layer comprising the material different from the cladding layer comprises Al x Ga 1-x As (0 ⁇ x ⁇ 0.4).
  • (3) and (4) are a device with an oscillation wavelength of 0.9 ⁇ m to 1.05 ⁇ m or a device with an oscillation wavelength of from 780 to 870 nm.
  • the former is used, for example, as a fiber amplifier for optical communication and the latter is used as an industrial or medical laser.
  • the control is easy. For example, this is the same composition as that of the etch stopper layer of the ridge structure.
  • a semiconductor laser device in which the cladding layer in direct concern with the invention comprises Al x Ga y In 1-x-y P (0 ⁇ x ⁇ 0.53 and 0 ⁇ y ⁇ 0.52) and the layer comprising the material different from the cladding layer comprises either Ga 0.52 In 0.48 P or Al z Ga 1-z As (0 ⁇ z ⁇ 1).
  • the semiconductor laser device of the material system described above is a device with an oscillation wavelength for excitation of from 630 to 690 nm used as an industrial or medical laser.
  • the control is easy.
  • this is the same composition as that for the etch stopper layer of the ridged structure.
  • a semiconductor laser device in which the cladding layer in direct concern with the invention comprises Al x Ga 1-x N and the layer comprising the material different from the cladding layer comprises Al x′ Ga 1-x′ N (0 ⁇ x′ ⁇ x ⁇ 1).
  • the semiconductor laser device of the material system is a device with an oscillation wavelength for excitation of from 280 to 410 nm used as industrial or medical laser.
  • the control is easy.
  • FIG. 1 is a cross-sectional view showing a structure of a semiconductor laser according to a first embodiment of the present invention.
  • the cross section corresponds to a plane crossing the proceeding direction of light.
  • an n-GaAs buffer layer 2 of 0.5 ⁇ m thick
  • an n-cladding layer 6 as a first cladding layer
  • a multi-quantum well structure active layer 7 a p-AlGaInP cladding layer 8 of 0.2 ⁇ m thick
  • a p-AlGaInP cladding layer 10 of 1.3 ⁇ m thick
  • a p-GaInP contact layer 11 of 0.05 ⁇ m thick are epitaxially grown successively by a metal organic vapor phase epitaxy method.
  • the n-cladding layer 6 comprises specifically an n-AlGaInP layer 3 of 1 ⁇ m thick, a portion 4 having a periodical structure comprising ten n-GaInP layers each of 3 nm thick and nine n-AlGaInP layers each of 120 nm thick, and an-AlGaInP layer 5 of 0.2 ⁇ m thick.
  • the n-AlGaInP layer is used and a plurality of thin layers of n-GaInP layers different in the composition from AlGaInP is inserted in the n-cladding layer 6 in view of the structure.
  • GaInP has a higher refractive index than AlGaInP.
  • the oscillation wavelength is set at 650 nm to 660 nm.
  • the multi-quantum well structure active layer 7 comprises three unintentionally-doped compressive strained GaInP quantum well layers each of 5 nm thick, four tensile strained AlGaInP quantum barrier layers each of 4 nm thick, and non-strained AlGaInP optical separate confinement layer of 20 nm thick above and below them. Further, the compositions of AlGaInP contained in the cladding layers 3 , 4 , 5 , 8 , and 10 are the same, i.e., (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P. Making the composition constituting each of the layers the same can improve controllability for the composition in the manufacturing step.
  • a ZnO solid diffusion source is vapor deposited. Then, by applying an annealing treatment at a temperature from 500° C. to 600° C., a Zn impurity diffusion region is formed at regions corresponding to the cavity facets. After formation of the impurity diffusion region, the diffusion source is removed. Then, a ridge stripe structure is formed by a usual method. By way of the photolithographic step and the etching step, the layer 10 and the layer 11 are removed by etching till the layer 9 , to form a stripe.
  • an n-AlInP current blocking layer 12 of 1.0 ⁇ m thick is put to selective area growth by an MOVPE method.
  • trenches for reducing the device capacitance are formed on both sides of the stripe by the photolithographic step and the etching step (not illustrated).
  • an insulative film mask 14 is formed, a p-side electrode 15 and an n-side electrode 16 are vapor deposited and then devices are cut out by cleaving scribe.
  • the device oscillates at a wavelength of 650 nm to 660 nm, the kink free maximum optical power of 300 mW was attained at a temperature of 80° C. and the variation in the polarization direction was stabilized within ⁇ 3 degrees.
  • reference numeral 50 denotes a light emission spot of the laser device.
  • Reference numeral 51 denotes a spot size in the vertical direction of the spot.
  • the spot size in the vertical direction of the laser is 0.88 ⁇ m.
  • the distance between each of the thin n-GaInP layers inserted in the n-cladding layer 6 is defined by the thickness 120 nm of the n-AlGaInP layer. Accordingly, the thickness is 120 nm.
  • the value 120 nm is less than 220 nm, i.e., 1 ⁇ 4 of 0.88 ⁇ m of the spot size in the vertical direction of the laser.
  • the near field pattern monotonously decreases as receding from the active layer as show in FIG. 8A to be described later.
  • FIG. 2 is a cross-sectional view showing the structure of a semiconductor laser according to a second embodiment of the invention. While this embodiment is different in the structure concerning the optical confinement, the semiconductor stacked structure regarding the semiconductor laser is the same as that in Example 1 described above.
  • the cross sectional view of FIG. 2 corresponds to a plane crossing the proceeding direction of light.
  • a n-type GaAs buffer layer 2 of 0.5 ⁇ m thick
  • an n-cladding layer 6 a multi-quantum well structure active layer 7
  • a p-AlGaInP cladding layer 8 of 0.2 ⁇ m thick
  • a GaInP etch stopper layer 9 of 5 nm thick
  • a p-GaInP contact layer 11 of 0.05 ⁇ m thick are successively grown epitaxially by the MOVPE method.
  • the n-type cladding layer 6 comprises an n-AlGaInP layer 3 of 1.5 ⁇ m thick, a portion 4 having a periodical structure of eight n-GaInP layers each of 2 nm thick and seven n-AlGaInP layers each of 100 nm thick, and an n-AlGaInP layer 5 of 0.2 ⁇ m thick.
  • the spot size is 0.91 ⁇ m.
  • the distance between each of the thin n-GaInP layers inserted in the n-cladding layer 6 is defined by the thickness of the n-AlGaInP layer. Accordingly, the thickness is 100 nm.
  • the value 100 nm is less than 227.5 nm, i.e., 1 ⁇ 4 of 0.91 ⁇ m of the spot size in the vertical direction of the laser.
  • the near field pattern decreases monotonously as receding from the active layer as shown in FIG. 8A to be described later.
  • the multi-quantum well structure active layer 7 comprises three unintentionally-doped compressive strained GaInP quantum well layers each of 5 nm thick, four tensile strained AlGaInP quantum barrier layers each of 4 nm thick, and non-strained AlGaInP optical separation confinement layer of 10 nm thick above and below them. Further, the compositions of AlGaInP contained in the cladding layers 3 , 4 , 5 , 8 , and 10 are the same, i.e., (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P. Making such a composition constituting each of the layers the same can improve controllability for the composition in the manufacturing step.
  • a ZnO solid diffusion source is vapor deposited. Then, by applying an annealing treatment at a temperature of 500° C. to 600° C., a Zn impurity diffusion region is formed at a region corresponding to the cavity facets. After formation of the impurity diffusion region, the diffusion source is removed. Then, a ridge stripe structure is formed by a usual method. By way of the photolithographic step and the etching step, the layer 10 and the layer 11 are removed by etching to the layer 9 , to form a stripe.
  • trenches for reducing the device capacitance are formed on both sides of the stripe by the photolithographic step and the etching step (not illustrated).
  • an insulative film mask 14 is formed, a p-side electrode 15 and an n-side electrode 16 are vapor deposited and then devices are cut out by cleaving scribe.
  • the device oscillates at a wavelength of 650 nm to 660 nm, the kink free maximum optical output of 300 mW was attained at a temperature of 80° C. and the variation in the polarization direction was stabilized within ⁇ 2 degrees.
  • FIG. 3 is a cross-sectional view showing the structure of a semiconductor laser according to a third embodiment of the invention. In this embodiment, the materials are changed but the stacked structure of the semiconductor is the same as those described above.
  • the cross-sectional view of FIG. 3 corresponds to a plane crossing the proceeding direction of light.
  • an n-GaAs buffer layer 2 of 0.5 ⁇ m thick an n-cladding layer 20 comprising an n-AlGaAs layer 17 of 1 ⁇ m thick, a portion 18 having a periodical structure of ten n-GaAs layers each of 7 nm thick and nine n-AlGaAs layers each of 100 m thick and an n-AlGaAs layer 19 of 0.2 ⁇ m thick, an n-GaAs optical separate confinement layer 21 of 30 nm thick, unintentionally-doped compressive strained In 0.16 Ga 0.84 As quantum well active layer 22 of 10 nm thick, an n-GaAs optical separation confinement layer 23 of 30 nm thick, a p-AlGaAs cladding layer 24 of 1.5 ⁇ m thick, and a p-Ga
  • the n-cladding layer 20 has an n-AlGaAs layer 17 of 1 ⁇ m thick, a portion 18 having a periodical structure of ten n-GaAs layers 10 each of 7 nm thick and nine n-AlGaAs layers each of 100 nm thick, and an n-AlGaAs layer 19 of 0.2 ⁇ m thick.
  • composition for AlGaAs contained in each of the cladding layers 17 , 18 , 19 , and 24 is the same, i.e., Al 0.3 Ga 0.7 As. Making the composition constituting each of the layers the same can improve the controllability for the composition in the manufacturing step.
  • the layer 24 is removed by etching to the midway by way of a photolithographic step and an etching step to form a stripe.
  • an insulative film 26 is formed, a p-side electrode 27 and an n-side electrode 28 are vapor deposited and devices are cut out by cleaving scribe.
  • the device oscillates at a wavelength of 980 nm to 1080 nm, a maximum king free optical output of 800 mW is attained at a temperature of 80° C., and the variations in the direction of polarization were stabilized within ⁇ 2 degrees.
  • the vertical spot size is 1.1 ⁇ m.
  • the distance between each of the thin layers n-GaAs layers inserted in the n-cladding layer 20 is defined by the thickness of the n-AlGaAs layer.
  • the thickness the n-AlGaAs layer is 100 nm.
  • the value is less than 275 nm, i.e., 1 ⁇ 4 of 1.1 ⁇ m of the vertical spot size.
  • FIG. 4 is a cross-sectional view showing the structure of a semiconductor laser according to a fourth embodiment of the invention.
  • the cross-section corresponds to a plane crossing the proceeding direction of a light.
  • the n-cladding layer 33 in this embodiment comprises a portion 31 having a structure formed by alternately stacking six n-InGaAsP layers with the thickness increasing as 5, 6, 7, 8, 9, and 10 nm toward the active layer and five n-InP layers each of 200 nm thick, and an n-InP layer 32 of 0.2 ⁇ m thick.
  • a first conduction type cladding layer is configured such that the change of the optical output in the near field of the semiconductor laser device is made continuous.
  • the near field is substantially equal to that in FIG. 8A . That is, the change of the optical output of the near field is continuous.
  • the spot size is 1.8 ⁇ m and the thickness of an insertion region 31 is 1.6 ⁇ m.
  • the wavelength for the composition of InGaAsP in the stacked structure 31 is made the same as that of the barrier layer constituting the quantum well of the active laser 35 .
  • the layer 30 is removed by etching to the midway by way of a photolithographic step and an etching step to form a stripe. Then, a semi-insulative InP current blocking layer 39 is selectively grown by an MOVPE method to bury the stripe. Then, an insulative film 40 is formed, a p-side electrode 41 and an n-side electrode 42 are vapor deposited and devises are cut out by cleaving scribe.
  • the device oscillates at a wavelength of 1400 nm to 1480 nm, a maximum kink free optical output reaches 1 W at a temperature of 25° C., and the variations in the direction of polarization was stabilized within ⁇ 2 degrees.
  • the basic structure is the same as that of the first embodiment described above and is different in that the structure of the n-cladding layer is constituted as described below.
  • the cladding layer comprises a n-AlGaInP layer 3 of 0.46 ⁇ m thick, a portion 4 having a periodical structure comprising ten n-GaInP layers each of 3 nm thick and nine n-AlGaInP layers each of 180 nm thick, and an n-AlGaInP layer 5 of 0.2 ⁇ m thick. Further, the total thickness of the n-AlGaInP layer 3 , the stacked portion 4 of the semiconductor layers and the n-AlGaInP layer 5 is made the same as that of the n-cladding layer 6 in Embodiment 1.
  • a stacked body 4 of 1.65 ⁇ m thick formed by alternately stacking ten n-GaInP layers each of 3 nm thick and nine n-AlGaInP layers each of 180 nm thick is inserted between the n-AlGaInP layer 3 of 0.46 ⁇ m thick as the first cladding layer and the n-AlGaInP layer 5 of 0.2 ⁇ m thick as the second cladding layer.
  • the stacked body 4 has a larger thickness than the total thickness, 0.66 ⁇ m, of the first and the second cladding layers. In this case, the vertical spot size in the vertical direction is 0.88 ⁇ m.
  • a semiconductor laser device comprising a first conduction type semiconductor substrate, a first conduction type cladding layer formed over the substrate, an active layer formed over the cladding layer, and a second conduction type cladding layer formed over the active layer, in which
  • a plurality of layers each having a refractive index higher than the refractive index of the first conduction type cladding layer and comprising a material different from the first conduction type cladding layer are inserted in the first conduction type cladding layer at a distance of less than 1 ⁇ 4 of the vertical spot size over a range larger than the vertical spot size.
  • a semiconductor laser device comprising a first conduction type semiconductor substrate, a first conduction type cladding layer formed over the substrate, an active layer formed over the cladding layer, and a second conduction type cladding layer formed over the active layer, in which
  • a plurality of layers each having a refractive index higher than the refractive index of the first conduction type cladding layer and comprising a material different from the first conduction type cladding layer are inserted in the first conduction cladding layer over a range larger than the vertical spot size, and the inter-layer distance is arranged such that the optical pattern decreases monotonously as receding from the active layer.
  • a semiconductor laser device according to any one of items 1 to 4, wherein the refractive index of the layer comprising the material different from that of the cladding layer is lower than the refractive index of the layer having the highest refractive index constituting the active layer.
  • a semiconductor laser device according to any one of items 1 to 4, wherein the film thickness of the layer comprising the material different from that of the cladding layer is not greater than the film thickness of the layer having the highest refractive index constituting the active layer.
  • the second conduction type cladding layer has a ridged shape and comprises a second conduction type lower cladding layer and a second conduction type upper cladding layer in the form of the ridged shape over the active layer, in which an etch stopper layer used for fabricating the second conduction type upper cladding layer into the ridged shape is disposed just above the second conduction type lower cladding layer.
  • a semiconductor laser device wherein the refractive index of the layer comprising the material different from that of the cladding layer is substantially equal to the refractive index of the layer having the highest refractive index constituting the etch stopper layer.
  • a semiconductor laser device in which a structure formed by alternately stacking a layer having a refractive index higher than that of the first and the second cladding layers, and a thickness of about several tens of atomic layers and comprising a material different from that of the first and the second cladding layer, and a layer having a refractive index substantially equal to that of the first or the second cladding layer is inserted between the first and second cladding layers which are put between the semiconductor substrate and the active layer, with the thickness of the structure being larger than the total thickness of the first and the second cladding layer.
  • a semiconductor laser device according to item 10, wherein the number of layers comprising the material different from that of the cladding layer is 4 or more.
  • a semiconductor laser device according to any one of items 1 to 11, wherein the cladding layer comprises either InP or In 1-z-w Ga z Al w As and the layer comprising the material different from that of the cladding layer comprises In 1-x Ga x As y P 1-y (0 ⁇ x ⁇ 0.47 and 0 ⁇ y ⁇ 1) or In 1-z′-w′ Ga z′ Al w′ As (0 ⁇ z ⁇ z′ ⁇ 0.47 and 0 ⁇ w′ ⁇ w ⁇ 0.48) different in the composition from In 1-z-w Ga z Al w As.
  • a semiconductor laser device according to any one of items 1 to 11, wherein the cladding layer comprises Al x Ga 1-x As (0 ⁇ x ⁇ 1), and the layer comprising the material different from the cladding layer comprises GaAs.
  • a semiconductor laser device according to any one of items 1 to 11, wherein the cladding layer comprises Ga 0.52 In 0.48 P, and the layer comprising the material different from that of the cladding layer comprises Al x Ga 1-x As (0 ⁇ x ⁇ 0.4).
  • a semiconductor laser device according to any one of items 1 to 11, wherein the cladding layer comprises Al x Ga y In 1-x-y P (0 ⁇ x ⁇ 0.53 and 0 ⁇ y ⁇ 0.52) and the layer comprising the material different from that of the cladding layer comprises either Ga 0.52 In 0.48 P, or Al z Ga 1-z As (0 ⁇ z ⁇ 1).
  • a semiconductor laser device according to any one of items 1 to 11, wherein the average composition of the cladding layer comprises Al x Ga 1-x N and the layer comprising the material different from that of the cladding layer comprises Al x′ Ga 1-x′ N (0 ⁇ x′ ⁇ x ⁇ 1).
  • a plurality of layers each of high refractive index different in the composition from the cladding layer are introduced and dispersed over a range wider than the spot size, to direct light closer to the lower cladding layer, thereby making it possible to enlarge the cut off range and reduce optical absorption in the contact layer above the upper cladding layer.
  • the direction of polarization can be stabilized.
  • likelihood of the design can be improved by utilizing the composition that is detectable during inspection in the semiconductor laser manufacturing process. Accordingly, a structure in which the optical pattern decreases monotonously as receding from the active layer can be selected and a single peak optical spot necessary for reading an optical disk can be obtained.
  • p-AlGaInP cladding layer 11 . . . p-GaInP contact layer, 12 . . . n-AlInP current blocking layer, 13 . . . p-GaAs contact layer, 14 . . . insulative film mask, 15 . . . p-side electrode, 16 . . . n-side electrode, 17 . . . n-AlGaAs layer, 18 . . . a portion having a periodical structure of ten n-GaAs layers and nine n-AlGaAs layers, 19 . . . n-AlGaAs layer, 20 . . .
  • n-cladding layer 21 . . . GaAs optical separation confinement layer, 22 . . . unintentionally-doped compressive strained InGaAs quantum well active layer, 23 . . . GaAs optical separation confinement layer, 24 . . . p-AlGaAs cladding layer, 25 . . . p-GaAs contact layer, 26 . . . insulative film, 27 . . . p-side electrode, 28 . . . n-side electrode, 29 . . . n-InP substrate, 30 . . . n-InP buffer layer, 31 . . .
  • portion having a structure formed by alternately stacking six n-InGaAsP layers and five n-InP layers, 32 . . . n-InP layer, 33 . . . n-cladding layer, 34 . . . InGaAsP optical separation confinement layer, 35 . . . unintentionally-doped compressive strained InGaAsP quantum well active layer, 36 . . . InGaAsP optical separation confinement layer, 37 . . . p-InP cladding layer, 38 . . . p-InGaAs contact layer, 39 . . . semi-insulative InP current blocking layer, 40 . . .
  • insulative film 41 . . . p-side electrode, 42 . . . n-side electrode, 43 . . . optical guiding layer, 44 . . . GaAs cap layer, 50 . . . light emission spot, 51 . . . spot size in the vertical direction of the light emission spot.

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EP2454619A4 (en) 2009-07-17 2016-01-06 Hewlett Packard Development Co NON PERIODIC FILTER REFLECTORS WITH FOCUSING STRENGTH AND METHOD FOR THE PRODUCTION THEREOF
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WO2011093893A1 (en) 2010-01-29 2011-08-04 Hewlett-Packard Development Company, L.P. Optical devices based on non-periodic sub-wavelength gratings
JP5139555B2 (ja) * 2011-04-22 2013-02-06 住友電気工業株式会社 窒化物半導体レーザ、及びエピタキシャル基板
JP2013033930A (ja) * 2011-06-29 2013-02-14 Sumitomo Electric Ind Ltd Ｉｉｉ族窒化物半導体素子、及び、ｉｉｉ族窒化物半導体素子の製造方法

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